This invention relates to aeration systems for diffusing air into liquids utilizing submerged diffusers and, more particularly, to an aeration system in which access to the submerged diffusers is facilitated.
In many aeration systems for treatment of wastewater such as described, for example, in the Von Nordenskjold et al. Patents Nos. 4,287,062, 4,797,272 and 5,472,611, the disclosures of which are incorporated herein by reference, purification of wastewater in a basin is effected by aerating the water with air bubbles emitted by submerged diffusers located adjacent to the bottom of the basin. In those systems the diffusers are suspended by downcomers from flexible floating air lines which supply air under pressure to the diffusers. As air bubbles emerge from the diffusers, the resulting turbulence causes the diffusers to move back and forth in the basin which in turn causes the flexible aeration lines to move along the surface of the water so that the entire aeration region of the basin is swept by the diffusers. In other submerged diffuser aeration systems, the diffusers normally rest on the bottom of the basin.
Periodically, it is necessary to obtain access to such submerged diffusers at the bottom of the basin for servicing. This might be accomplished with considerable difficulty by manually grasping downcomers by which the diffusers are suspended from a floating air line and attempting to pull the diffusers up to the surface of the water by moving the downcomers to a horizontal orientation or by grappling for submerged diffusers resting on the bottom of the basin. When the diffusers have been raised they must be held at the surface of the water while the necessary servicing is effected and, if inadvertently released, the same procedure must be followed to raise them again from their submerged position at the bottom of the basin.
The Tharp Patent No. 5,133,876 proposes a solution to this problem by providing a flexible retrieval rope tied at its lower end to the diffuser and secured at the surface by tying it to the aeration line or to a float which floats on top of the wastewater. Such retrieval lines, however, still require manual effort and are subject to loss or damage from debris in the wastewater or deterioration with time.
The Murphy Patent No. 5,316,671 discloses aeration diffuser trains consisting of bladders supporting flexible air lines having suspended diffusers. The bladders are inflated to hold the air line at the surface of the water and suspend the diffusers above the bottom during operation but, to avoid damage to aeration lines and their suspended diffusers resulting from floating debris in wastewater being treated when the diffusers are inoperative, the bladders may be deflated to pennit the air line to sink until it is below the surface of the water and the diffusers rest on the bottom of the basin. When the air line is intended for operation again, the bladders are reinflated, raising the air line to the surface of the water and suspending the diffusers away from the bottom of the basin. The submerged diffusers, however, must still be raised manually to the surface of the water in the manner described above for servicing.